SM465 HD or R700 ??

SCullison · November 29, 2001

I have a 1984 GMC Pickup with a strong 350 engine, R700 transmission and a broken NP208 transfer case.

I have found an NP205 that the seller suggests would be preferrable to the 208 for me to install.

I found an NP208 that was behind an SM465 transmission. (Will it bolt up to my R700?)

The fellow offered to sell me the SM465 and NP208 combination.

What is the best option? I don't want to have to re-invent anything or go through any major hassles but am a relatively capable mechanic. Can someone with knowledge and/or experience in this area please warn me of the plus side and minus side of these various options before I spend the money?

What will be involved if I switch, or should I just keep looking for the exact duplicate of my broken unit?

Steven

Kansas Kid · December 2, 2001

The automatic tranny you have now, its a 4 speed with OD correct? I think you are talking about a 700R-4, but I'm not sure.

This is kind of hard to recommend what you should do, because these transfer cases used several different numbers of input splines, so you need to pick out just the right case to fit your bill.

The NP205 (gear driven) was used from 1971 to 1991. The 1971-79 NP205 was only found mated to the TH350 and the SM465 transmission. For 1-ton vehicles between 1979 to 1984/85, GM used a TH400 and the SM465. The TH400 was equipped with a female 32 spline input, while the SM465 retained the male 10 spline input. These model transfer cases had a figure-eight front bolt pattern.

In 1985 to 1991 vehicles, GM started using a different version of the NP205. The input spline for both the TH400 and the SM465 transmissions was a female 32 spline, and the front bolt pattern changed to circular bolt pattern.

The NP208 (chain driven) also has a circular bolt pattern, and had either a 27 or 32 spline input. In 1988, GM next introduced the NP241 chain-driven transfer case. This transfer case, as far as bolt patterns and splines are concerned, is identical to the NP208.

The main thing you need to be concerned with is finding a transfer case with the correct number of splines, and go from there. Once you get that far, you should be able to get an adapter to fit any of the above transfer cases to your automatic.